Field of the Invention
The invention relates in general to a single-layer multi-touch sensing electrode group, and more particularly to a single-layer multi-touch sensing electrode group of a touch panel for enhancing linearity and accuracy of the touch panel.
Description of the Related Art
FIG. 1 shows a conventional single-layer multi-touch sensing electrode group. The sensing electrode group can be divided into two kinds—transmitting electrodes and receiving electrodes. As shown in FIG. 1, the transmitting electrodes include a sensing electrode 105, a sensing electrode 110, a sensing electrode 120 and a sensing electrode 130; the receiving electrodes include a sensing electrode 140, a sensing electrode 150, a sensing electrode 160 and a sensing electrode 170. In general, the transmitting electrodes are equal in size. That is, the sensing electrode 105, the sensing electrode 110, the sensing electrode 120 and the sensing electrode 130 have equal areas. Further, the receiving electrodes are also equal in size. That is, the sensing electrode 140, the sensing electrode 150, the sensing electrode 160 and the sensing electrode 170 have equal areas. The sensing electrode 105, the sensing electrode 110, the sensing electrode 120 and the sensing electrode 130 are directly connected to a control unit (not shown) by connecting lines. The receiving electrodes may further be divided into two types—a first type (an electrode denoted R1 in FIG. 1), including the sensing electrode 140 and the sensing electrode 160 connected by a connecting line 115, and a second type (an electrode denoted R2 in FIG. 1), including the sensing electrode 150 and the sensing electrode 170 connected by a connecting line 125. It should be noted that, the number of electrodes of a touch panel is not limited to the exemplary values in the diagram, and both of the transmitting electrodes and the receiving electrodes may be further extended towards the lower part of the diagram to include more electrodes. The receiving electrodes of the first type are connected to the control unit from the sensing electrode 140 via the connecting lines, and the receiving electrodes of the second type are similarly connected to the control unit from the sensing electrode 150 via the connecting lines.
When the touch panel detects a touch event, the control unit transmits a signal to the transmitting electrodes (the sensing electrode 105, the sensing electrode 110, the sensing electrode 120 and the sensing electrode 130), and the position of the touch event is calculated according to the capacitance changes detected between the receiving electrodes and the transmitting electrodes. For example, when a touch event 180 occurs in a region among the sensing electrode 110, the sensing electrode 140 and the sensing electrode 150 (assuming that the position of the touch event 180 in the y direction is between the sensing electrode 140 and the sensing electrode 150), the sensing electrode 140 and the sensing electrode 150 theoretically sense capacitance changes having equal values. Thus, the control unit may calculate the position of the touch event. However, the proximity of the touch event further includes the connecting line 115 in addition to the sensing electrode 140 and the sensing electrode 150. The connecting line 115 affects the distribution of electric charge and further affects mutual capacitance changes between the sensing electrode 110 and the sensing electrode 140 as well between the sensing electrode 110 and the sensing electrode 150. More specifically, as the connecting line 115 is connected to the sensing electrode 140, the connecting line 115 may be regarded as an extension of the sensing region of the sensing electrode 140. As such, the sensing electrode 140 not only reacts more sensitively to the touch event 180 but also hinders the sensing electrode 150 from sensing the touch event 180 to certain extent. As a result, the touch position of the touch event 180 determined by the control unit is higher than (closer to the sensing electrode 140) the actual position, hence affecting the linearity and accuracy of the touch panel.